Biologics are commonly employed to promote bone growth in medical applications including fracture healing and surgical management of spinal disorders. Spine fusion is often performed by orthopedic surgeons and neurosurgeons alike to address degenerative disc disease and arthritis affecting the lumbar and cervical spine, to correct deformities caused by scoliosis, and to repair instability due to spondylolisthesis. Additionally, the techniques of spinal fusion may be applied to treat arm or leg pain caused by compressed spinal nerves. Historically, autogenous bone grafting, commonly taken from the iliac crest of the patient, has been used to augment fusion between vertebral levels.
One protein that is osteogenic and commonly used to promote spine fusion is recombinant human bone morphogenetic protein-2 (rhBMP-2). Small molecules have also been use to induce bone growth. Oxysterols form a large family of oxygenated derivatives of cholesterol that are present in the circulation, and in human and animal tissues. Oxysterols have been found to be present in atherosclerotic lesions and play a role in various physiologic processes, such as cellular differentiation, inflammation, apoptosis, and steroid production. Some naturally occurring oxysterols have robust osteogenic properties and can be used to grow bone. The most potent osteogenic naturally occurring oxysterol, 20(S)-hydroxycholesterol, is both osteogenic and anti-adipogenic when applied to multipotent mesenchymal cells capable of differentiating into osteoblasts and adipocytes.
One such oxysterol is Oxy133 or (3S,5S,6S,8R,9S,10R, 13S, 14S,17S) 17-((S)-2-hydroxyoctan-2-yl)-10, 13-dimethylhexadecahydro-1H-cyclopenta[a]phenanthrene-3,6-diol, which exhibits the following structures:

A variety of materials have been suggested for the treatment of bone defects. In addition to traditional bone grafting, a number of synthetic bone graft substitutes have been used or explored, including several matrix materials.
To conduct bone growth effectively, implant materials derive benefit from the presence of substantial scaffolding material such as biocompatible ceramics or other mineral scaffolds. Such mineral materials are generally hard, and/or brittle substances. The incorporation of substantial levels of mineral particles into matrix materials, particularly if the mineral particles are granules or other relatively large particles, may be difficult because the large particles of hard minerals tend to disrupt the matrix mass such that it is readily broken or eroded away, and lacks cohesiveness desired for handling prior to implant and for persistence after implant. This may present problems in achieving effective bone growth into and through the desired implant volume, due to migration or separation of the scaffolding particulates. Additionally, carrier scaffolds with high amounts of ceramics are rigid and typically cannot fit into irregularly shaped bone defects. Further, implant materials fail to provide an effective slow release of biologics for the treatment of bone defects.
Therefore, there exists a need for improved implants which provide an effective slow release of an osteogenic agent, such as an oxysterol encapsulated in polymer microspheres. Additionally, there is a need to not only have mineral particles, but also maintain the desired combination of malleability and cohesiveness.